Once a hungry fox went about in search of food and reached a vineyard. He stopped near one of the trees that bore beautiful ripe grapes which were hanging in bunches. His mouth watered. He thought that he would eat the ripe grapes to satisfy his hunger.
So he tried to catch hold of the grapes. He jumped as high as possible to hold at least one of the bunches which was not so high. But still it was beyond his reach. When his repeated efforts failed to get even a single grape, he was upset.
So he consoled himself by thinking that these grapes must be sour, which he should not taste. And it is better to leave the vineyard and look for food somewhere else. So the fox went away.